Control valve having a curved spring band serving as a non-return valve

ABSTRACT

A control valve, in particular a proportional valve for controlling a device for adjusting the rotation angle position of a camshaft with respect to a crankshaft of an internal combustion engine, including a hollow-cylindrical valve housing ( 1 ), which has a plurality of openings ( 2 ) that are arranged circumferentially in a radial plane for connecting to a pressure medium connection (P) and can be closed via a non-return valve ( 4 ) designed as a curved spring band ( 3 ). According to the invention, the openings ( 2 ) arranged in a radial plane are arranged at different angle distances to each other, and the shape and the rotation angle position of the curved spring band ( 3 ) serving as a non-return valve ( 4 ) is matched thereto.

FIELD OF THE INVENTION BACKGROUND

The invention relates to a control valve, in particular to a proportional valve for controlling a device for adjusting the rotational angle position of a camshaft with respect to a crankshaft of an internal combustion engine. A control valve of this type has a valve housing which is of hollow-cylindrical design and is intended for receiving an axially displaceable control piston, the axial displacement of which causes a pressure medium connection to be connected to or disconnected from at least one working connection. For this purpose, the outer circumferential side of the control piston has control edges which interact with valve housing openings arranged on the circumferential side.

Control valves of the abovementioned type are used, for example, for controlling a device for the rotational angle position of a camshaft with respect to a crankshaft of an internal combustion engine. The camshaft serves to actuate the gas exchange valves, the opening or closing time of which is to be set depending on the current range of performance characteristics of the engine, in particular depending on the current rotational speed or load thereof, in order to optimize the engine efficiency. For this purpose, the rotational angle position of the camshaft with respect to the crankshaft is adjusted via a device which is actuatable electrically, hydraulically or pneumatically. The control valve provided in the present case is intended to be usable in particular for controlling such a hydraulically actuatable adjusting device.

EP 1 291 563 A2 discloses a control valve of the above-mentioned type having a non-return valve integrated in the valve housing. The non-return valve consists of an annularly curved spring band which serves at the same time as a closing element and as a spring element. The curved spring band is placed into an annular groove formed on the outer or inner circumferential side of the valve housing such that said spring band undergoes elastic deformation upon pressurization in the opening direction and opens up bores formed in the valve housing or in a sleeve surrounding the valve housing for the passage of an operating medium while said spring band resumes the original shape thereof and closes the bores upon pressurization in the closing direction.

The non-return valve serves to avoid the transmission of pressure pulsations which are operationally induced to arise in the camshaft adjuster and—without a non-return valve—could pass back via the working and pressure oil connections of the control valve into the pressure oil circuit. Since, as a rule, further components, in particular secondary components, such as chain adjusters, etc., are connected to the same pressurized oil circuit, back flow of the operating medium may result in damage to the further components. At the same time, the non-return valve serves to support pressure pulsations, thus increasing the torsional rigidity, i.e. the positional stability of the adjusting device.

SUMMARY

It is the object of the present invention to develop a control valve having a non-return valve in such a manner that a defined opening and closing of the non-return valve is ensured over the long term. In addition, the control valve is intended to be constructed in a simple manner and to be producible cost-effectively.

To achieve the object, a control valve having one or more of the features of the_invention is proposed. Advantageous developments of the invention are provided below.

For connection to a pressure medium connection P, the valve housing, which is of hollow-cylindrical design, of the proposed control valve has a plurality of openings which are arranged circumferentially in a radial plane and are closable via a non-return valve designed as a curved spring band. According to the invention, the openings arranged in a radial plane are arranged at different angular distances from one another, and the shape and the rotational angle position of the curved spring band serving as the non-return valve are matched to said angular distances. The different angular distances between the openings formed in the valve housing result in a non-rotationally-symmetrical arrangement of the openings and therefore in a non-rotationally-symmetrical design of the valve housing. In this case, an arrangement of the openings at different angular distances from one another is also to be understood as meaning an arrangement in which only one angular distance is designed to be larger or smaller than the other angular distances. For example, one angular distance can be selected to be of a size such that a concentration of the openings occurs in a sector extending over a certain angular range while a further sector is optionally formed without openings. The concentration of the openings on one side or in a certain sector region of the valve housing predetermines a preferred flow direction of the operating medium and therefore an orientation of the curved spring band, in which the spring band and the openings interact in an optimum manner. This has to apply in particular if—as provided—the shape and the rotational angle position of the curved spring band are furthermore matched to the asymmetrical arrangement of the openings. A high throughflow rate and a simultaneously small pressure drop can therefore be brought about even given a small opening stroke of the spring band.

In order to match the shape of the spring band to the asymmetrical arrangement of the openings in the valve housing, provision is made, according to a preferred embodiment of the invention, for the curved spring band serving as a non-return valve to have an open oval shape. It is ensured by the open shape that the spring element can be sufficiently elastically deformed in order to produce an opening stroke. The oval shape substantially predetermines an orientation of the spring band with respect to the openings formed in the valve housing. Furthermore, given an appropriate design of a spring band receptacle, the oval shape can be used for securing the rotational angle position of the spring band with respect to the valve housing, thus ensuring an optimum interaction of openings and spring band even over the long term.

Furthermore preferably, the valve housing for receiving the curved spring band in the region of the openings has different wall thicknesses such that an at least partially encircling groove having a varying groove depth is formed on the outer or inner circumferential side of the valve housing. The spring band is preferably arranged in the interior of the valve housing. In this case, a groove into which the spring band can be placed is furthermore formed preferably on the inner circumferential side in the region of the openings. The groove depth of the groove varies such that the groove base firstly rises, then drops. The groove depth may also peter out entirely such that the groove base corresponds to the inner wall of the valve housing. The groove is then not of encircling design. The valve housing preferably has an oval shape in cross section in the region of the groove in a manner corresponding to the shape of the spring band such that the latter bears in an encircling manner against the groove base. In addition, the corresponding oval shape of the spring band and groove brings about a securing of the rotational angle position of the spring band. The formation of a groove for receiving the spring band furthermore has the advantage that, due to the form-fitting connection, the axial position of the spring band is also secured.

As an alternative, the curved spring band serving as the non-return valve may also, however, be inserted into a groove on the outer circumferential side of the valve housing or into a groove on the inner circumferential side of a receiving bore of a camshaft or of a cylinder head and interact in a corresponding manner with the openings of the valve housing and/or with openings of the receiving bore. In these cases too, the spring band is preferably placed into a groove, the groove depth of which varies in order to achieve an oval groove shape in the cross section of the valve housing or in the receiving bore, said groove shape being matched to the oval shape of the spring band.

Furthermore preferably, the width of the groove, which is provided for receiving the spring band, in the valve housing substantially corresponds to the width of the spring band. As a result, the axial position of the spring band is fixed. However, this may also mean that the groove width is optionally selected to be slightly larger in order to facilitate the insertion of the spring band.

When the non-return valve is designed as a curved spring band, the spring band serves at the same time as a closing element and as a spring element. The spring band therefore combines the functions of closing element and spring element in one component. Furthermore, the opening and closing characteristics of the non-return valve are adjustable via the spring strength of the curved spring band. The spring strength is predetermined in particular by the hinge strength of the spring band. The hinge strength may also be varied, for example, over the circumference of the curved spring band.

The pressure medium connection P is advantageously designed as an at least partially encircling groove arranged on the outer circumferential side of the valve housing. For the sake of simplicity, the groove may be designed as an annular groove. In a corresponding manner, further annular grooves may be arranged on the outer circumferential side of the valve housing, said annular grooves forming further connections, for example the working connections A and B.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention is described in more detail below with reference to the drawings, in which:

FIG. 1 shows a side view and a top view of a curved spring band of a control valve according to the invention,

FIG. 2 shows a longitudinal section and a cross section through a valve housing of a control valve according to the invention,

FIG. 3 shows a longitudinal section through the valve housing of FIG. 2 with the spring band inserted upon pressurization in the opening direction, and

FIG. 4 shows a longitudinal section through the valve housing of FIG. 2 with the spring band inserted upon pressurization in the closing direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 show the essential elements of a control valve according to the invention, namely a spring band 3 usable as a non-return valve 4, and a valve housing 1, each in an individual illustration. In the exemplary embodiment of FIGS. 3 and 4, the spring band 3 is inserted into a groove 5 formed on the inner circumferential side of the valve housing 1 such that the spring band 3 bears against the groove base of the groove 5 under a certain radial prestress.

As can be gathered from FIG. 1, the spring band 3 usable as the non-return valve 4 is curved to form an oval shape such that the ends of the spring band 3 are spaced apart from each other. The distance between the ends or the opening of the oval shape ensures that the spring band 3 is elastically deformable within the groove 5. The width of the spring band 3 is constant and is matched to the width of the groove 5.

As FIG. 2 shows, an ovally shaped groove 5 is formed in a manner corresponding to the oval shape of the spring element 3 on the inner circumferential side of the valve housing 1 (see cross section of the valve housing) in the region of openings 2 which serve to hydraulically connect a pressure medium connection P, which is designed as an encircling groove 6, to working connections A and B. In this case, the openings 2 are arranged circumferentially at different angular distances from one another in such a manner that the groove 5 does not have any openings 2 over a certain angular range. A main flow direction of the operating medium is therefore predetermined, said flow direction, together with the shape of the groove 5, predetermining a certain orientation of the spring band 3. This ensures optimum interaction of openings 2 and spring band 3. In addition, the groove 5 secures the installed position of the spring band 3 against axial displacement and against rotation.

The functioning of the non-return valve 4 is as follows:

Upon pressurization of the spring band 3 in the opening direction (see FIG. 3) by operating medium being supplied via the pressure medium connection P, the spring band 3 is pressed radially inward, wherein said spring band undergoes elastic deformation and opens up the openings 2. Even at a small opening stroke of the spring band 3, a high throughflow rate can be obtained with little pressure drop, i.e. low losses, since the arrangement of the openings 2 is concentrated on the region about the pressure medium connection or the port P. Depending on the axial position of a control piston (not illustrated), the operating medium passes via the opened-up openings 2 to further openings 7 which serve for the hydraulic connection to a working connection A or B, said working connections being designed as an annular groove corresponding to the pressure medium connection P.

However, if the pressure ratios are such that the spring band 3 is acted upon in the closing direction by a pressure force which is greater than the prevailing operating pressure, for example due to pressure pulsations, the operating medium can flow back via the working connections A or B, and the spring band 3 is placed against the base of the groove 5 again and thereby closes the openings 2 formed in the groove 5.

LIST OF REFERENCE NUMERALS

-   1 Valve housing -   2 Openings -   3 Spring band -   4 Non-return valve -   5 Groove -   6 Groove -   7 Openings 

1. A control valve for controlling a device for adjusting a rotational angle position of a camshaft with respect to a crankshaft of an internal combustion engine, comprising a hollow-cylindrical valve housing and, for connection to a pressure medium connection (P), the housing valve has a plurality of openings which are arranged circumferentially in a radial plane and are closable via a non-return valve formed by a curved spring band the openings which are arranged in the radial plane are arranged at different angular distances from one another, and a shape and a rotational angle position of the curved spring band serving as the non-return valve are matched to said angular distances.
 2. The control valve as claimed in claim 1, wherein the curved spring band serving as the non-return valve has an open oval shape.
 3. The control valve as claimed in claim 1, wherein the valve housing for receiving the curved spring band in a region of the openings has different wall thicknesses such that an at least partially encircling groove having a varying groove depth is formed on an outer or inner circumferential side of the valve housing.
 4. The control valve as claimed in claim 3, wherein a width of the groove substantially corresponds to a width of the spring band.
 5. The control valve as claimed in claim 1, wherein opening and closing characteristics of the non-return valve are adjustable via a spring strength of the curved spring band.
 6. The control valve as claimed in claim 1, wherein the pressure medium connection (P) is formed as an at least partially encircling groove arranged on an outer circumferential side of the valve housing. 